The objectives of the studies proposed are to quantitatively describe the control characteristics of pulmonary and systemic hemodynamics by the arterial baroreceptors. By utilizing chronically instrumented, awake dogs, the effects of the inhalational agents, nitrous oxide and halothane, upon the baroreceptor control of pulmonary hemodynamics will be determined. In addition, the effects of induced systemic renal hypertension upon the above relationships will be investigated. Electromagnetic flow probes will be chronically implanted on the main pulmonary artery and the ascending aorta. By means of a pneumatic occlusion device on the brachiocephalic artery, carotid sinus hypotension will be produced. From the aortic and pulmonary artery pressure and flow responses, values of aortic and pulmonary input impedance will be determined, together with the various components of the corresponding hydraulic power. The pulmonary and systemic responses to brachiocephalic occlusion will subsequently be studied in the above dogs during 50% nitrous oxide, 70% nitrous oxide, halothane in oxygen and halothane in 70% nitrous oxide. As a terminal procedure mean carotid sinus pressure will be changed in the isolated sinused before and after division of the aortic depressor nerves and following bilateral cervical vagotomy to eliminate aortic baroreceptor afferents and any remaining cardiopulmonary vagal afferents, respectively. The above acute and chronic studies will subsequently be repeated in dogs in which systemic hypertension has been induced following unilateral renal artery constriction and in a further group of dogs in which the affected kidney has been removed and a remission of the systemic hypertension has occurred.